Digital PCR based an end point measurement
that works by random distribution of the sample into
discrete partitions.
6
This concept was started in 1992 by
Sykes et al. to quantify the total number of initial targets
present in a sample using limiting dilution of PCR, and
Poisson distribution statistics. The PCR has been opti-
mized to provide an all-or-none end point at very low DNA
target numbers that means some portions of these reac-
tions contain the target molecule (positive) while others
contain no template (negative), and these partitions are
thermally cycled to end point, and then lead to determine
the fraction of positive partitions to calculate copy number
without standards.
6
Currently there are three approaches
employed by commercially available digital PCR sys-
tems. The
fi
rst approach is micro
fl
uidic dPCR
19
based
on standard 5’-nuclease probe (TaqMan) chemistry and
primer–probe design rules by using single used micro
fl
u-
idic chip to split the sample into the nanoliter individual
cDNA partitions, then detection using a PCR end-point
scan after thermocycled.
20
The second approach, called
BEAMing dPCR based on 4 principle including beads,
emulsion, ampli
fi
cation, and magnetic.
21-22
Recently there
is another new approach that uses water-in-oil droplet,
called droplet digital PCR (ddPCR) system in 96-well plate